8.1 Metabolism Flashcards
What is metabolism?
The sum total of all reactions that occur within an organism in order to maintain life
What causes most chemical changes in a cell?
A series of reactions
What controls each steps of series of reactions?
specific enzymes
Why do metabolic pathways allow for a greater level of regulation?
As the chemical change is controlled by numerous intermediates
What are metabolic pathways typically organised into?
Chains or cycles of enzyme catalysed reactions
What does every chemical reaction require in order to proceed?
A certain amount of energy
What is the energy needed in order to proceed called?
Activation energy
How do enzymes speed up the rate of a biochemical reaction?
By lowering the activation energy
What happens when an enzyme binds to a substrate?
It stresses and i the bonds in the substrate
What happens when the energy level of the substrates is reduced to the transitionary state?
Less energy is needed to convert into a product thus the reaction happens faster
What is an exergonic reaction?
If the reactants contain more energy than the products, the free energy is released into the system
What is an endergonic reaction?
If the reactants contain less energy than the products, free energy is lost to the system
What type of reactions are exergonic?
Catabolic
Why are exergonic reactions usually catabolic?
As energy is released from broken bonds within a molecule
What type of reactions are endergonic reactions?
Anabolic
Why are endergonic reactions normally anabolic?
As energy is required to synthesise bonds between molecules
What is an enzyme inhibitor?
A molecule that disrupts the normal reaction pathway between an enzyme and a substrate
What are the two types of enzyme inhibitors?
Competitive or non competitive
What do enzyme inhibitors prevent?
The formation of an enzyme substrate complex and thus any product
Why may the inhibition of enzymes be reversible or irreversible?
Depending on the specific effect of the inhibitor being used
What is an example of a competitive inhibitor?
Relenza
What is an example of a non competitive inhibitor?
Cyanide as poison
What do substrates do in a normal reaction?
Bind to an enzyme to form an enzyme substrate complex
What results in enzyme substrate specifity?
The fact that the shape and properties of active site and substrate are complementary
During a normal enzyme reaction what happens when binding occurs?
The active site undergoes a conformational change to optimally interact with the substrate
During a normal enzyme reaction, what does the conformational change do?
Destabilises chemical bonds in the substrate which lowers the activation energy
What is a consequence of enzyme interaction?
The substrate is converted into product at an accelerated rate
What is competitive inhibition?
Involves a molecule other than the substrate, binding to the enzymes active site
Why is the inhibitor molecule able to bind to the active site?
As it is structurally and chemically similar to the substrate
What does the competitive inhibitor do?
Blocks the active site and stops substrate binding
How can you reduce the effects of the inhibitor?
Increasing substrate concentration
What is non competitive inhibition?
Involves a molecule binding to a site other than the active site
What is the site that a non competitive inhibitor binds to?
An allosteric site
What does the inhibitor binding to the allosteric site cause?
A conformational change to the enzymes active site
In non competitive inhibition what does the change in the active site cause?
The active site and substrate aren’t complementary and thus the substrate cannot bind
Why does increasing the substrate levels not mitigate non competitive inhibitors effects?
As the inhibitor is not in direct competition with the substrate
What is end product inhibition?
A form of negative feedback by which metabolic pathways can be controlled
What is the function of end product inhibition?
To ensure levels of an essential product are always tightly regulated
In end product inhibition, what happens if product levels build up?
The product inhibits the reaction pathway and decreases the rate of further product formation
In end product inhibition, what happens if product levels drop?
The reaction pathway will proceed uninterrupted and the rate of product formation will increase
In end product inhibition, what does the final product do?
Inhibits an enzyme from an earlier step in the sequence
In end production inhibition, what does the product bind to?
An allosteric site
In end product inhibition, what does the product do?
Temporarily inactivates the enzyme
In end product inhibition, what happens as the enzyme can no longer function?
The reaction sequence is halted and the rate of product formation is decreased
What is isoleucine?
An essential amino acid
Where do you have to get isoleucine from and why?
From food sources as it is not synthesised by the body
In plants and bacteria where is isoleucine synthesised from?
Theronine
How many steps is the isoleucine reaction pathway?
Five
What happens in the first step of the isoleucine reaction pathway?
Threonine is converted into an intermediate compound by an enzyme
During the five step reaction pathway what does isoleucine function as?
A non competitive inhibitor
How is the production of isoleucine an example of end product inhibition?
An excess production of isoleucine inhibits further synthesis
What does the end product inhibition feedback of isoleucine ensure?
That isoleucine production does not cannibalise available stocks of theronine
How can the rate of an enzyme catalysed reaction be calculated and plotted according to?
The time taken for the reaction to proceed
What are the two ways time taken can be measured according to?
Amount of product formed or amount of substrate consumed
What is reaction rate the inverse of?
Time taken
What is the formula for rate of reaction?
1/time taken
What factors influence the rate of an enzyme catalysed reaction?
Temperature
pH
Substrate concentration
How do both competitive and non competitive inhibitors reduce the rate of reaction?
By limiting the amount of uninhibited enzyme available for reaction
Can the maximum rate of enzyme reaction still be achieved with a competitive inhibitor?
Yes but a higher substrate concentration is required
Can the maximum rate of enzyme activity be achieved with non competitive inhibitors?
No it is reduced
When comparing the graphs of the effect of inhibition, from top to bottom what is the order?
Uninhibited
Competitive inhibitor
Non competitive inhibitor
What is malaria?
A disease caused by parasitic protozoans
What does the life cycle of the parasite require?
Both a human and mosquito host
How is malaria transmitted?
Via mosquito bites
What is responsible for the maturation and development of the parasite in both human and mosquito host?
Specific enzymes
What has scientists sequencing the genome of infectious species of plasmodium done?
Helped determine the parasites proteome
What has learning about the parasites proteome done?
Helped identify enzymes involved in parasitic metabolism as potential targets for inhibition
What are the enzymes identified in the proteome screened against and why?
A bioinformatic database of chemicals to identify potential enzyme inhibitors
What may happened when a promising compound is identified? (malaria)
It may be chemically modified to improve its binding affinity and lower its toxicity
What is another way anti malarial medications can be synthesised?
Rational drug design
What does rational drug design involve?
Computer modelling techniques to invent a compound that functions as inhibitor
In rational drug design, how is a complimentary compound synthesised?
Using complementary chemistry
